Optical retro-modulators provide a unique means to transfer free space optical data without the need to generate and broadcast laser light, thereby saving much size, weight, and power at the retro-modulation and of an optical communication link between the optical retro-modulator and laser interrogator. Additionally, optical retro-modulators can be included in an optical “tag” with an optical receiver (which can detect and decode data received by modulated light from the laser interrogator, thereby enabling two-way communication between the optical tag and the laser interrogator.
Traditional optical tags, however, suffer various trade-offs. In particular, trade-offs exist between optical aperture, field of view (FOV) and modulator size, the latter of which limits the speed. Typically, in view of these trade-offs, longer-range optical systems (e.g., optical systems in which the distance between a laser interrogator and an optical tag exceeds 500 m) typically resorts to “cooperative” free space optical communication systems in which an optical tag is replaced with a second laser interrogator, resulting in a laser interrogator at both ends of optical communication. Problematically, however, the setup is impractical in many scenarios.